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BlenderMCP

by opslon

get_polyhaven_categories

Retrieve available categories for Polyhaven assets like HDRI, textures, or models to filter and organize 3D content in Blender.

Instructions

Get a list of categories for a specific asset type on Polyhaven.

Parameters:

  • asset_type: The type of asset to get categories for (hdris, textures, models, all)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
asset_typeNohdris

Implementation Reference

  • The get_polyhaven_categories function is registered as an MCP tool and handles the retrieval of categories from Polyhaven by communicating with a Blender instance.
    @mcp.tool()
    def get_polyhaven_categories(ctx: Context, asset_type: str = "hdris") -> str:
        """
        Get a list of categories for a specific asset type on Polyhaven.
        
        Parameters:
        - asset_type: The type of asset to get categories for (hdris, textures, models, all)
        """
        try:
            blender = get_blender_connection()
            # Check PolyHaven status directly
            status = blender.send_command("get_polyhaven_status")
            if not status.get("enabled", False):
                return "PolyHaven integration is disabled. Select it in the sidebar in BlenderMCP, then run it again."
            result = blender.send_command("get_polyhaven_categories", {"asset_type": asset_type})
            
            if "error" in result:
                return f"Error: {result['error']}"
            
            # Format the categories in a more readable way
            categories = result["categories"]
            formatted_output = f"Categories for {asset_type}:\n\n"
            
            # Sort categories by count (descending)
            sorted_categories = sorted(categories.items(), key=lambda x: x[1], reverse=True)
            
            for category, count in sorted_categories:
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states it 'Get[s] a list' which implies a read-only operation, but doesn't specify if it's safe, requires authentication, has rate limits, or what the output format looks like. For a tool with zero annotation coverage, this leaves significant behavioral gaps unaddressed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is appropriately sized and front-loaded, starting with the core purpose followed by parameter details. Both sentences earn their place by providing essential information without redundancy. It's efficient but could be slightly more structured, such as separating usage notes from parameters.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's low complexity (one parameter) and lack of annotations or output schema, the description is minimally adequate. It covers the purpose and parameter semantics but misses behavioral context like response format or error handling. For a simple read tool, it's functional but could be more complete by adding output details or usage scenarios.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds meaningful semantics beyond the input schema, which has 0% description coverage. It explains that 'asset_type' is for specifying the type of asset to get categories for, and lists possible values (hdris, textures, models, all), clarifying usage that isn't in the schema. With only one parameter, this compensates well for the low schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'Get' and resource 'list of categories for a specific asset type on Polyhaven', making the purpose understandable. It distinguishes from siblings like 'search_polyhaven_assets' by focusing on categories rather than assets, though it doesn't explicitly contrast with other Polyhaven tools. The purpose is specific but could be more distinct from related operations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites, such as needing to know asset types before searching, or when to choose this over 'search_polyhaven_assets' for browsing categories. Usage is implied through the parameter description but lacks explicit context or exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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